Dependence of odontogenic abscess on meteorological parameters: truth or myth?

It is still a common belief among dental practitioners that odontogenic abscesses are somehow linked to meteorological parameters. We investigated the influence of different meteorological parameters on the type of surgical abscess treatment (intra- versus extraoral incision) as a measure of the weather-dependent severity of infection. In this retrospective cohort study, we analyzed 841 patients who presented at our outpatient clinic with an odontogenic abscess between 2004 and 2013. We found no statistical dependence between intra- versus extraoral abscess incision with regard to temperature, atmospheric pressure, or relative air humidity. The annual distribution of abscesses was even, and the number of abscesses with greater or lesser mean values of each meteorological parameter did not differ significantly. Our results showed no statistical relationship between meteorological parameters and intra- or extraoral abscess incisions. Our analysis supports the assumption that the theorized relationship between odontogenic abscesses and meteorological parameters remains a myth.


Introduction
It is still a common belief among dental practitioners and oral surgeons that the incidence of oral abscesses is somehow linked to weather conditions, such as temperature or atmospheric pressure. Nissen et al. [1] in 1978 proposed a relationship between low barometric pressure and odontogenic abscesses. Harlfinger et al. [2] supported this hypothesis in 1981 and even found a specific relationship between the occurrence of odontogenic abscesses and specific changes in weather from anticyclonic to cyclonic conditions (high barometric pressure to low barometric pressure). Even in 2015, Seemann et al. [3] published a report that low barometric pressure increases the number of patients with dental abscesses. In contrast, Ristow et al. [4] proclaimed in the same year that "a dental myth finally bites the dust," and that there is no relationship between weather conditions and odontogenic abscesses. Interestingly, the majority of publications on this topic originate from German-speaking countries, possibly reflecting the deep rootedness of this common belief in those particular cultural regions.
In general, medical meteorology is a vast field of research with controversial discussions on different topics. For example, in 2015, Nguyen et al. [5] discovered a relationship between the exposure to drier air and lower temperature and the onset of atrial fibrillation among patients with cardiac disease. As described by Yilmaz et al. [6], there also appears to be a relationship between high temperatures and low humidity on the occurrences of migraine headache. In 2014, Kozka et al. [7] claimed that weather factors had no impact on abdominal aortic ruptures, and that patient survival was dependent more on national holidays and the time of day. Busowski et al. [8] reported in 1995 that the incidence of pyelonephritis during pregnancy is not related to any climatic factor, contradicting another common belief that various disease states and pregnancy-related conditions are linked to meteorological factors [8]. Therefore, the question remains: do meteorological factors influence medical conditions, particularly odontogenic abscesses?
Following the path of truth in medical metrology, we retrospectively analyzed 841 patients with odontogenic abscesses who were treated at the Department of Oral and Maxillofacial Surgery Hannover Medical School, between 2004 and 2013. Our hypothesis was that meteorological parameters would not influence the incidence of odontogenic abscesses treated by an intraoral versus an extraoral approach in our population. Because we could not include a control group in our study, we analyzed these two different surgical approaches, as they are typically associated with a less (intraoral incision) or a more severe (extraoral incision) disease pattern.

Data source
The analyzed sample consisted of usable, retrospective data from 841 patients with odontogenic abscesses who were treated at the Department of Oral and Maxillofacial Surgery, Hannover Medical School, Germany, between 2004 and 2013. Only the patients with complete medical records were included in this study, leading to the sample size of 841. All information was gathered by an in-depth analysis of the digital medical records. The meteorological data during this time period was acquired for Hannover Herrenhausen and provided by the Institute of Meteorology and Climatology of the Leibniz University, Hannover.

Measurements and evaluations
Patients' sex, age, antibiotic therapy, abscess location, and International Statistical Classification of Diseases and Related Health Problems version 10 (ICD-10) codes were documented. The surgical treatment was defined as either an intra-or extraoral abscess incision, a combination of both, which was considered an extraoral incision or tooth removal only without an extra incision. The meteorological parameters including temperature, relative air humidity, daily precipitation level, and daily wind peak velocity were sourced for day 0 before the primary presentation, and the atmospheric pressure was sourced for days 7, 5, 2, and 0 before the primary presentation; these data were used in the statistical calculations.

Statistical analysis
All statistical analyses were performed using SigmaPlot version 13.0 (Systat Software, San Jose, CA, USA) and SPSS version 25.0 (IBM, Armonk, NY, USA). The analyses included descriptive statistics, cross-tabulations with Pearson's chisquare test to assess if there is a relationship between meteorological parameters and type of surgical abscess treatment, and one-way analysis of variance to assess any variations between the two surgical groups and the meteorological parameters. A p value of < 0.05 was considered statistically significant.

Patient characteristics
Of the 841 patients, 397 were women (47%) and 444 were men (53%). In total, 540 and 310 patients exhibited abscesses in the lower and upper jaws, respectively (15 had abscesses in both jaws). The specific distribution of abscesses following the ICD-10 is shown in Table 1. Patients were aged between 1 and 96 years (mean age, 39.0 ± 21.9 years), and 538 intraoral, 217 extraoral, and 52 combined incisions were performed. In 546 patients, tooth removal was necessary during treatment, thus causing some patients to undergo multiple incisions. A total of 807 patients were treated with an extra-or intraoral incision; the remaining 34 patients only underwent tooth removal. Six patients underwent intraoral incision elsewhere, outside the study center. A total of 406 (48%) patients were treated under general anesthesia, and 435 (52%) under local anesthesia. All patients received antibiotic therapy, with patients on more than one drug. The most frequently used antibiotic was penicillin (728), followed by clindamycin (116), metronidazole (132), and other antibiotics (4). The mean hospitalization time was 5.9 ± 3.9 days.

Statistical analysis
There was no statistically significant relationship between the temperature (p = 0.52), atmospheric pressure (p = 0.79), or relative air humidity (p = 0.85) and intra-versus extraoral abscess incisions. Moreover, analysis of the mean atmospheric pressure fluctuation starting 7 days before abscess treatment (mean standard deviation of atmospheric pressure) revealed no statistically significant association between the extent of atmospheric pressure fluctuation and intra-versus extraoral abscess incisions (p = 0.92). The number of cases of abscesses above or below the mean temperature, mean atmospheric pressure, or mean atmospheric pressure deviation was not significantly higher or lower (Table 2). In addition, there were no statistically significant differences (p = 0.77) with regard to the monthly distribution of abscesses (Fig. 1).

Discussion
In 2011, Kloss-Brandstätter et al. [9] published a retrospective review of 1090 patients who were treated for acute pain in the oral cavity at the outpatient dental clinic in Innsbruck, Austria. They found that daily deviation from the average atmospheric pressure, but not the air pressure itself, significantly influenced oral cavity pain. Until then, barodontalgia was mostly known to occur as a result of diving or flight conditions and was supposedly linked to much higher barometric pressure differences than atmospheric pressure deviations [10]. Because oral pain is often associated with a dental infection [11], we speculated whether the severity of oral abscesses (represented by the treatment choices, i.e., extra-versus intraoral incision) could also be directly linked to atmospheric pressure or atmospheric pressure changes. Surprisingly, there was no evidence of any influence in our analyzed population. In 1998, Keller et al. [12] examined 2111 patients with odontogenic infections and found a statistically significant higher prevalence during winter and spring. According to the principles of physical medicine, cases of infections should be more during periods of a higher temperature, e.g., summer, but it appears that these rules do not apply to the human body. They speculated that high temperature differences, e.g., between indoors and outdoors, or winter and spring, could have an impact on the autonomic nervous system and consequently influence the immune system, making people more vulnerable to infections. Nevertheless, they concluded that there was no reasonable correlation between temperature and incidence of odontogenic abscesses, without considering other pathophysiological and meteorological parameters into account. In agreement, this effect could not be found in our population. The distribution of abscesses was even throughout the year.
The defense against infections is dependent on multiple factors such as age, smoking, and secondary illnesses [13,14], and the pathogenicity of bacteria responsible for  odontogenic infections varies from simple external factors (e.g., temperature) to internal patient factors such as immunodeficiency. Therefore, many independent variables influence the development of odontogenic infections [15], and these should be considered in a larger study. Because of the retrospective study design, unfortunately, it was not possible to include more potential confounding factors. Further prospective studies might offer more opportunities for a deeper analysis of the pathogenesis of odontogenic abscesses with regard to meteorological parameters.

Conclusion
Our results showed no statistical relationship between meteorological parameters and intra-or extraoral abscess incisions. For our analyzed population, the influence of meteorological parameters on odontogenic abscesses remains, for the time being, a myth.
Funding Information Open Access funding provided by Projekt DEAL.

Compliance with ethical standards
Conflict of interest The authors declare that they have no conflict of interest.
Ethical approval This retrospective study was approved by the ethics committee of the Hannover Medical School. The 1964 Helsinki declaration and its later amendments or comparable ethical standards were followed in this study.
Informed consent All patients provided written consent for publication of their data.
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